Crosslinked organopolysiloxane and method for producing same, mist suppressant, and solvent-free silicone composition for release paper

ABSTRACT

Provided are: a crosslinked organopolysiloxane which has properties intermediate between a dimethylpolysiloxane oil and a gel-like crosslinked siloxane; and a method for producing the crosslinked organopolysiloxane. An oil-like organopolysiloxane which is produced by: adding a compound having a siloxane unit represented by formula (3) to a gel-like silicone, wherein the gel-like silicone is produced by a hydrosilylation reaction of an organopolysiloxane having an alkenyl group with an organohydrogenpolysiloxane having a hydrogen atom bonded to a silicon atom in the presence of a platinum-group metal catalyst; and then equilibrating the resultant product with an acid or alkali catalyst. 
       R 1   2 SiO 2/2   (3)
 
     (R 1  represents a group selected from a monovalent hydrocarbon group having no aliphatic unsaturated bond and an alkenyl group represented by the formula: —(CH 2 ) a —CH═CH 2  (wherein a represents a numerical value of 0 to 6), and the average polymerization degree of formula (3) is 3 to 2,000.)

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of copending application Ser. No.15/320,386, filed on Dec. 20, 2016, which was filed as PCT InternationalApplication No. PCT/JP2015/066207 on Jun. 4, 2015, which claims thebenefit under 35 U.S.C. § 119(a) to Patent Application No. 2014-128294,filed in Japan on Jun. 23, 2014, all of which are hereby expresslyincorporated by reference into the present application.

TECHNICAL FIELD

This invention relates to a crosslinked organopolysiloxane and to amethod for producing the same. The invention also relates to a mistsuppressant for use such as by addition in order to reduce the amount ofmist generated by the coater head when coating a solventless siliconecomposition for release paper onto a paper, plastic film or other basematerial with a high-speed roller, and to a solventless siliconecomposition for release paper formulated with this mist suppressant.

BACKGROUND ART

Gel-like crosslinked organopolysiloxanes are used, for example, incosmetics and in junction coatings for electrical wiring, but are allsolid substances that lack flowability. Hence, they do not dissolve insolvents and so a long grinding operation is required to formulate thesein cosmetics or resins.

Silicone oil dispersions of silicone gels are used in cosmetics. Suchproducts are obtained by first creating a solid silicone gel via anaddition reaction, and then grinding up the gel while dispersing it in asilicone oil. This production method is troublesome to carry out.Moreover, in the solid silicone gel, even if unreacted functional groupsare present near the regions that have become solid due to the reaction,the reaction proceeds no further. As a result, even when the samestarting materials are used, the crosslink density differs each timethat production is carried out, making the physical properties difficultto control.

In plastics, a silicone oil or silicone gum having a high degree ofpolymerization is dispersed in the resin and used to increase theflowability during molding or for such purposes as to prevent blemishesor to confer slip properties. Silicone oils with a low degree ofpolymerization have a flowability increasing effect and exhibitexcellent slip properties, but because the silicone oil bleeds out ontothe surface, the surface becomes slippery. Hence, gum-like siliconeshaving a high degree of polymerization are used, but it takes a lot oftrouble to uniformly disperse such silicones, such as by masterbatchingbeforehand.

Moreover, because most of the silicone added gets buried within theresin, only a portion takes part in action at the surface, resulting ina poor efficiency. On the other hand, when a solid silicone gel or resinis used, given the many ingredients that accumulate within the resin andalso their poor compatibility with the resin, dispersion is poor, whichoften lowers the mechanical strength. Moreover, the surface modifyingeffects are poor.

No methods for synthesizing compounds having physical propertiesintermediate to those of silicone gels and silicone oils have beenreported in the literature.

Also, in order to prevent bonding and sticking between base materials ofpaper, plastic or the like and pressure-sensitive adhesive materials, acured film of a organopolysiloxane composition has hitherto been formedon the surface of the base material, thereby imparting releaseproperties. The method of forming a peelable film by an additionreaction provides excellent curability and can accommodate a variety ofpeeling property requirements ranging from low-speed peeling tohigh-speed peeling, and thus is widely used as a method of forming acured film of organopolysiloxane on a base material surface.

The types of organopolysiloxane compositions used in this method offorming a peelable film by an addition reaction include one typeobtained by dissolving an organopolysiloxane composition in an organicsolvent, another type obtained by dispersing an organopolysiloxanecomposition in water using an emulsifying agent so as to form anemulsion, and a solventless type in which the composition consistssolely of organopolysiloxane. However, because the solvent type has thedrawback of being harmful to the human body or the environment, from thestandpoint of safety, a switch is underway from solvent-typecompositions to solventless-type compositions. Also, becausesolvent-type and emulsion-type compositions require the removal ofsolvent or water at the time of application, the transfer roller usedfor application cannot be set to a high speed. In addition, insolvent-type compositions, high-speed application is impossible owingalso to the danger of ignition. In the case of solventless-typecompositions, because there is no solvent to be removed by evaporationand the flash point is high, during mass production, high-speedapplication is carried out, increasing the productivity. However, whencarrying out the high-speed application of solventless-typecompositions, misting arises. The various mist suppressants mentionedbelow have been proposed in order to solve this problem of misting.

The mist suppressant in JP-A 2006-290919 (Patent Document 1) is theproduct of a condensation reaction between a diorganopolysiloxane cappedat both ends with silanol groups and an organohydrogenpolysiloxane usinga tin catalyst.

The condensation reaction is difficult to control and so there aremarked differences by lot in the degree of polymerization of thereaction product. Although the mist-suppressing effect increases at ahigher degree of polymerization, a gel-like product forms, makingmixture into a silicone for release paper difficult. Conversely, at alow degree of polymerization, mixture into silicone for release paper iseasy, but the mist-suppressing effect decreases and the migration ofunreacted product sometimes occurs, which may result in a lower peelstrength. Also, a concern with tin catalysts is their toxicity; whenused in addition-curable silicone compositions for release paper, theyact as poisons for platinum catalysts and inhibit curing, making theiruse undesirable.

The mist suppressants in JP Nos. 5033293 and 5033294 (Patent Documents 2and 3) are obtained by adding, to a solventless silicone composition forrelease paper, a compound prepared by reacting beforehand, in thepresence of a platinum catalyst or the like, a mixture wherein either analkenyl group-containing siloxane or an organohydrogenpolysiloxane ispresent in large excess (SiH group/alkenyl group ratio is at least 4.6,or alkenyl group/SiH group ratio is at least 4.6). These patentpublications relate to addition reaction products endowed with amist-suppressing effect; having one of the starting materials be presentin a large excess lowers the molecular weight of the addition reactionproduct, enabling the viscosity to be held down. Also, following thecure, surplus functional groups react with the silicone composition forrelease paper, suppressing migration.

However, due to the platinum catalyst that remains within the mistsuppressant, when the SiH group/alkenyl group ratio is 4.6 or more,there is a high danger of dehydrogenation occurring over time. This mayalso have an influence on the cure, and irregularities in the crosslinkdensity depending on the site may arise. On the other hand, when thealkenyl group/SiH group ratio is 4.6 or more, the Sill group/alkenylgroup ratio of the silicone for release paper becomes low and thecrosslink density changes, resulting in a change in peel strength.

The mist suppressant in JP-A 2006-506509 (Patent Document 4) is acompound obtained by partially crosslinking a vinyl group-containing MQresin with a partially substituted hydrido-silicone produced byincompletely reacting a long-chain olefin with an organohydrido-siliconcompound.

Patent Document 4 sets out to render a Q unit-containing siloxane intoan oil-like substance. When MQ units are added to anorganohydrido-silicon compound, depending on the lot, gelling sometimesarises even when the formulation is the same, thus making the viscositydifficult to control. Also, in the addition reaction, the degree ofconversion for the vinyl group-containing MQ resin is low and, followingreaction completion, the reaction sometimes proceeds over time,resulting in a higher viscosity. On trying to increase the degree ofconversion for the vinyl group-containing MQ resin in the additionreaction, the amount of platinum catalyst rises, making it impossible toinclude the mist suppressant beforehand in the silicone composition forrelease paper and worsening the pot life even when the mist suppressantis added at the time of use.

JP-A 2006-506510 and JP-A 2006-508206 (Patent Documents 5 and 6) relateto star-branched polymers as mist suppressants for coatings.Star-branched polymers are reaction products obtained by adding avinylsiloxane or an unsaturated functional group-containing organiccompound to the product of an addition reaction between a modifiedorganohydrogenpolysiloxane having silicon-bonded hydrogen atoms and a Qunit (SiO_(4/2) unit)-containing vinylsiloxane.

A gel tends to form in these reaction products and, depending on theadhesiveness and olefin chain effects, the peel strength sometimesbecomes high.

The mist suppressant of JP-A 2010-150537 (Patent Document 7), which isincluded in a silicone composition for release paper, is a polymerobtained by an equilibration reaction between a branchedorganopolysiloxane oligomer containing Q units (SiO_(4/2) units) and adiorganosiloxane oligomer.

A Q unit-containing organopolysiloxane oligomer is difficult to producewhile controlling the molecular weight, and so there is a largedisparity by lot in the molecular weight. Hence, effecting uniformdispersion by equilibration is difficult, and constantly obtaining auniform equilibrated compound is a challenge.

JP-A 2010-502778 (Patent Document 8) includes, as a mist suppressant ina silicone-based coating ingredient (silicone composition for releasepaper), a branched polysiloxane component produced from a copolymer of:(a) an organosilicon compound having at least two unsaturatedhydrocarbon functional groups per molecule and (b) an organosiliconcompound having at least two silyl hydride functional groups permolecule.

This reaction product often forms a gel, and the presence of a siliconegel gives rise to surface irregularities and unevenness in the coatingfilm. Also, because platinum catalyst remains in the branchedpolysiloxane component, when silyl hydride functional groups remainwithin the branched polysiloxane component, dehydrogenation reactionsarise during storage, as a result of which the container may swell or,in extreme cases, burst. Moreover, in formulations where the amount ofregulator is low, this sometimes causes addition reactions to arise inthe silicone-based coating ingredient during dispersion.

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: JP-A 2006-290919

Patent Document 2: JP No. 5033293

Patent Document 3: JP No. 5033294

Patent Document 4: JP-A 2006-506509

Patent Document 5: JP-A 2006-506510

Patent Document 6: JP-A 2006-508206

Patent Document 7: JP-A 2010-150537

Patent Document 8: JP-A 2010-502778

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

In light of the above, the object of this invention is to provide acrosslinked organopolysiloxane which exhibits physical propertiesintermediate to those of a dimethylpolysiloxane oil and a gel-likecrosslinked siloxane. Another object is to provide a method forproducing such a crosslinked organopolysiloxane.

Further objects of the invention are to provide a mist suppressant whichis an additive for reducing the amount of mist generated when asolventless silicone composition for release paper is applied onto theroller of a coating machine and transferred by rotating the roller athigh speed, and a solventless silicone composition for release paper towhich this mist suppressant has been added.

Means for Solving the Problems

The inventor has conducted extensive investigations in order to achievethe above objects. As a result, he has discovered that a crosslinkedorganopolysiloxane which has flowability and exhibits physicalproperties intermediate to those of an oil and a gel can be stablyproduced from an oil-like organopolysiloxane prepared by adding acompound having siloxane units of formula (3) below to a gel-likesilicone obtained by a hydrosilylation reaction between anorganopolysiloxane having at least two alkenyl groups per molecule andan organohydrogenpolysiloxane having at least two silicone-bondedhydrogen atoms per molecule in the presence of a platinum group metalcatalyst, and equilibrating with an acid or alkaline catalyst.

The inventor also noticed that when the gel-like silicone prior toequilibration is formulated in a solventless silicone composition forrelease paper, the mist suppressing effect is high, but the presence ofgel-like silicone tends to give rise to surface unevenness of thecoating film and coating irregularities, resulting in a separator thatis commercially worthless.

On the other hand, in the above addition product, when an oil-likeproduct having few crosslink sites was used, the mist suppressing effectwas confirmed to be low, yet an excellent mist suppressing effect wasobtained by adding the crosslinked organopolysiloxane to a solventlesssilicone composition for release paper.

R¹ ₂SiO_(2/2)  (3)

In formula (3), each R¹ is the same or a different group selected fromamong monovalent hydrocarbon groups of 1 to 20 carbon atoms that have noaliphatic unsaturated bonds and alkenyl groups represented by—(CH₂)_(a)—CH═CH₂ (where the subscript “a” is 0 or an integer from 1 to6). The average degree of polymerization of the siloxane of formula (3)is from 3 to 2,000.

Accordingly, the invention provides the following crosslinkedorganopolysiloxane and method of preparation thereof, and also providesthe following mist suppressant and solventless silicone composition forrelease paper.

[1] A crosslinked organopolysiloxane comprising an organopolysiloxanewhich contains 0.1 to 50 moles of silethylene linkages per 1,000 molesof siloxane units and is obtained by adding, to a gel-like siliconeprepared by hydrosilylation of an organopolysiloxane having a structureof formula (1) below with an organohydrogenpolysiloxane having astructure of formula (2) below

M_(α)M^(Vi) _(β)D_(γ)D^(Vi) _(δ)T_(ε)T^(Vi) _(ζ)Q_(η)  (1)

M_(θ)M^(H) _(τ)D_(κ)D^(H) _(λ)T_(μ)T^(H) _(ν)  (2)

(wherein M is R₃SiO_(1/2), M^(Vi) is R₂PSiO_(1/2), D is R₂SiO_(2/2),D^(Vi) is RPSiO_(2/2), T is RSiO_(3/2), T^(Vi) is PSiO_(3/2), M^(H) isR₂HSiO_(1/2), D^(H) is RHSiO_(2/2), T^(H) is HSiO_(3/2) and Q isSiO_(4/2), each R being independently an unsubstituted or substitutedmonovalent hydrocarbon group of 1 to 12 carbon atoms that has noaliphatic unsaturated bonds and P being an alkenyl group represented by—(CH₂)_(a)—CH═CH₂ (where “a” is 0 or an integer from 1 to 6); and α, β,γ, δ, ε, ζ, η, θ, τ, κ, λ, μ, and ν are each independently 0 or apositive number, with the provisos that β, δ and ζ are not all 0,β+δ+ζ≥2, τ, λ and ν are not all 0, and τ+λ+ν≥2), a compound havingsiloxane units of formula (3) below

R¹ ₂SiO_(2/2)  (3)

(wherein each R¹ is the same or a different group selected from amongmonovalent hydrocarbon groups of 1 to 20 carbon atoms that have noaliphatic unsaturated bonds and alkenyl groups represented by—(CH₂)_(a)—CH═CH₂ (where “a” is 0 or an integer from 1 to 6); and anaverage degree of polymerization of the siloxane of formula (3) is from3 to 2,000 in the compound having siloxane units of formula (3)) andcarrying out equilibration.[2] The crosslinked organopolysiloxane of [1] wherein, in formula (1),1≤α+γ+ε+η≤1,000≤1,000 and, in formula (2), 1≤θ+κ+μ≤200.[3] The crosslinked organopolysiloxane of [2] wherein, in formula (1),1≤γ≤1,000 and, in formula (2), 1≤κ≤200.[4] The crosslinked organopolysiloxane of any one of [1] to [3], whereinthe compound having siloxane units of formula (3) is an organosiloxaneselected from among octamethyltetrasiloxane, decamethylpentasiloxane,linear siloxanes of the formula M₂D_(n) (M being an R₃SiO_(1/2) unit, Dbeing an R₂SiO_(2/2) unit, each R being independently an unsubstitutedor substituted monovalent hydrocarbon group of 1 to 12 carbon atomswhich has no aliphatic unsaturated bonds, and n being an integer from 0to 200) and branched siloxanes of the formula M_(2+m)D_(n)T_(m) (M, Dand n being the same as above, T being an RSiO_(3/2) unit, R being thesame as above, and m being an integer from 1 to 10).[5] The crosslinked organopolysiloxane of any one of [1] to [4], whereinthe organopolysiloxane of formula (1) has a weight-average molecularweight of 260 to 74,186 and the organohydrogenpolysiloxane of formula(2) has a weight-average molecular weight of 208 to 14,934.[6] A siloxane composition obtained by diluting the crosslinkedorganopolysiloxane of any one of [1] to [5] with a low-viscosityorganopolysiloxane having a viscosity at 25° C. of 1 to 400 mPa·s.[7] A mist suppressant comprising the crosslinked organopolysiloxane ofany one of [1] to [5] or the siloxane composition of claim 6.[8] A solventless silicone composition for release paper, comprising:

(A) 100 parts by weight of an organopolysiloxane having two or moresilicon-bonded alkenyl groups per molecule,

(B) 0.1 to 30 parts by weight of an organohydrogenpolysiloxane havingthree or more silicon-bonded hydrogen atoms per molecule,

(C) a catalytic amount of a platinum group metal catalyst, and

(D) 0.01 to 20 parts by weight of the mist suppressant of [7].

[9] A method of producing a crosslinked organopolysiloxane, comprisingthe steps of preparing a gel-like silicone by hydrosilylation of anorganopolysiloxane having the structure of formula (1) below with anorganohydrogenpolysiloxane having the structure of formula (2) below

M_(α)M^(Vi) _(β)D_(γ)D^(Vi) _(δ)T_(ε)T^(Vi) _(ζ)Q_(η)  (1)

M_(θ)M^(H) _(τ)D_(κ)D^(H) _(λ)T_(μ)T^(H) _(ν)  (2)

(wherein M is R₃SiO_(1/2), M^(Vi) is R₂PSiO_(1/2), D is R₂SiO_(2/2),D^(Vi) is RPSiO_(2/2), T is RSiO_(3/2), T^(Vi) is PSiO_(3/2), M^(H) isR₂HSiO_(1/2), D^(H) is RHSiO_(2/2), T^(H) is HSiO_(3/2) and Q isSiO_(4/2), each R being independently an unsubstituted or substitutedmonovalent hydrocarbon group of 1 to 12 carbon atoms that has noaliphatic unsaturated bonds and P being an alkenyl group represented by—(CH₂)_(a)—CH═CH₂ (where “a” is 0 or an integer from 1 to 6); and α, β,γ, δ, ε, ζ, η, θ, τ, κ, λ, and ν are each independently 0 or a positivenumber, with the provisos that β, δ and are not all 0, β+δ+ζ≥2, τ, and νare not all 0, and τ+λ+ν≥2); and subsequently adding to the gel-likesilicone a compound having siloxane units of formula (3) below

R¹ ₂SiO_(2/2)  (3)

(wherein each R¹ is the same or a different group selected from amongmonovalent hydrocarbon groups of 1 to 20 carbon atoms that have noaliphatic unsaturated bonds and alkenyl groups represented by—(CH₂)_(a)—CH═CH₂ (where “a” is 0 or an integer from 1 to 6; and anaverage degree of polymerization of the siloxane of formula (3) is from3 to 2,000 in the compound having siloxane units of formula (3)) andcarrying out equilibration so as to obtain an organopolysiloxane whichcontains 0.1 to 50 moles of silethylene linkages per 1,000 moles ofsiloxane units.

Advantageous Effects of the Invention

The crosslinked organopolysiloxane of the invention has physicalproperties intermediate between those of a dimethylsilicone oil and agel-like crosslinked siloxane, can be suitably used in variousapplications, such as silicone gels for cosmetics, and is particularlyeffective as a mist suppressant.

The mist suppressant of the invention, when added in a small amount to asolventless silicone composition for release paper, enables the amountof mist generated when transfer is carried out by the high-speedrotation of a roller to be greatly reduced.

Moreover, because the mist suppressant of the invention contains nosolid gel and does not include an active platinum group metal catalyst,even when mixed with an organohydrogenpolysiloxane having silicon-bondedhydrogen atoms, dehydrogenation does not arise and there is no crosslinkreaction-promoting effect over time. In addition, the mist suppressanthas an excellent mist suppressing effect.

EMBODIMENT FOR CARRYING OUT THE INVENTION

The crosslinked organopolysiloxane of the invention consists of anorganopolysiloxane (V) which contains 0.1 to 50 moles of silethylenelinkages per 1,000 moles of siloxane units and is obtained by adding acompound (IV) having siloxane units of formula (3) below to a gel-likesilicone (III) prepared by hydrosilylation of an organopolysiloxane (I)having a structure of formula (1) below and anorganohydrogenpolysiloxane (II) having a structure of formula (2) below,and carrying out equilibration.

M_(α)M^(Vi) _(β)D_(γ)D^(Vi) _(δ)T_(ε)T^(Vi) _(ζ)Q_(η)  (1)

M_(θ)M^(H) _(τ)D_(κ)D^(H) _(λ)T_(μ)T^(H) _(ν)  (2)

In formulas (1) and (2), M is R₃SiO_(1/2), M^(Vi) is R₂PSiO_(1/2), D isR₂SiO_(2/2), D^(Vi) is RPSiO_(2/2), T is RSiO_(3/2), T^(Vi) isPSiO_(3/2), M^(H) is R₂HSiO_(1/2), D^(H) is RHSiO_(2/2), T^(H) isHSiO_(3/2) and Q is SiO_(4/2). Each R is independently an unsubstitutedor substituted monovalent hydrocarbon group of 1 to 12 carbon atoms thathas no aliphatic unsaturated bonds, and P is an alkenyl grouprepresented by —(CH₂)_(a)—CH═CH₂ (wherein “a” is 0 or an integer from 1to 6). Also, α, β, □, δ, ε, ζ, η, θ, τ, κ, λ, and ν are eachindependently 0 or a positive number, with the provisos that (3, 6 and(are not all 0, β+δ+ζ≥2, τ, λ, and ν are not all 0, and τ+λ+ν≥2.

R¹ ₂SiO_(2/2)  (3)

In formula (3), each R¹ is the same or a different group selected fromamong monovalent hydrocarbon groups of 1 to 20 carbon atoms that have noaliphatic unsaturated bonds and alkenyl groups represented by—(CH₂)_(a)—CH═CH₂ (wherein “a” is 0 or an integer from 1 to 6). Thesiloxane of formula (3) has an average degree of polymerization of from3 to 2,000.

First, the organopolysiloxane (I) having a structure of formula (1)below and the organohydrogenpolysiloxane (II) having a structure offormula (2) below are described.

M_(α)M^(Vi) _(β)D_(γ)D^(Vi) _(δ)T_(ε)T^(Vi) _(ζ)Q_(η)  (1)

M_(θ)M^(H) _(τ)D_(κ)D^(H) _(λ)T_(μ)T^(H) _(ν)  (2)

In formulas (1) and (2), M, M^(Vi), D, D^(Vi), T, T^(Vi), M^(H), D^(H),T^(H) and Q are respectively the units shown below.

M: R₃SiO_(1/2),

M^(Vi): R₂PSiO_(1/2),

D: R₂SiO_(2/2),

D^(Vi): RPSiO_(2/2),

T: RSiO_(3/2),

T^(Vi): PSiO_(3/2),

M^(H): R₂HSiO_(1/2),

D^(H): RHSiO_(2/2),

T^(H): HSiO_(3/2),

Q: SiO_(4/2).

In these formulas, each R is independently an unsubstituted orsubstituted monovalent hydrocarbon group of 1 to 12 carbon atoms, andpreferably 1 to 6 carbon atoms, which has no aliphatic unsaturatedbonds. Illustrative examples include alkyl groups such as methyl, ethyl,propyl, butyl, pentyl, hexyl, octyl, decyl and dodecyl groups;cycloalkyl groups such as a cyclohexyl group; aryl groups such asphenyl, naphthyl and tolyl groups; and any of these groups in which someportion of the hydrogen atoms bonded to carbon atoms are substitutedwith halogen atoms, cyano groups, hydroxyl groups or the like. However,to lower the peel strength, it is preferable for at least 50 mol % ofthe total number of R groups to be methyl groups.

P is an alkenyl group represented by —(CH₂)_(a)—CH═CH₂ (wherein “a” is 0or an integer from 1 to 6), and is preferably —CH═CH₂.

α, β, γ, δ, ε, ζ, η, θ, τ, κ, λ, τ and ν are each independently 0 or apositive number. Here, β, δ and are not all 0; the sum β+δ+ζ is 2 ormore, preferably 2 to 10, and more preferably 2 to 5; τ, λ and ν are notall 0; and the sum τ+λ+ν is 2 or more, preferably 2 to 10, and morepreferably 2 to 5.

Also, α, γ, ε and η are not all 0 and, particularly from the standpointof the content of silethylene linkages, the sum α+γ+ε+η is preferably 1to 1,000, more preferably 10 to 500, and even more preferably 50 to 400.Here, from the standpoint of the content of silethylene linkages, γ inparticular is preferably 1 to 1,000, more preferably 10 to 500, and evenmore preferably 50 to 400. In addition, a is preferably 0 to 20, morepreferably from 0 to 10, and especially 0 to 5; ε is preferably 0 to 50,and especially 0 to 10; and η is preferably 0 to 5, and especially 0 to1.

In addition, θ, κ and μ are not all 0 and, similarly, from thestandpoint of the content of silethylene linkages, the sum θ+κ+μ ispreferably 1 to 200, more preferably 10 to 150, and even more preferably20 to 100. Here, κ is preferably 1 to 200, more preferably 10 to 150,and even more preferably 20 to 100; θ is preferably 0 to 20, morepreferably 0 to 10, and especially 0 to 5; and μ is preferably 0 to 50,and especially 0 to 10.

The organopolysiloxane (I) of formula (1) is an organopolysiloxanehaving at least 2, and preferably from 2 to 10, silicon-bonded vinylgroups per molecule.

The weight-average molecular weight of this organopolysiloxane ispreferably from 260 to 74,186, and more preferably from 408 to 7,586.When the weight-average molecular weight is too small, the alkaliequilibration reaction following the addition reaction may not fullyproceed; on the other hand, when it is too large, the gel may be softand sticky, making it difficult to handle. Here and below, theweight-average molecular weight can be measured as thepolystyrene-equivalent weight-average molecular weight by gel permeationchromatographic (GPC) analysis (solvent: toluene).

Specific examples of such organopolysiloxanes (1) include siloxaneshaving alkenyl groups at both ends, siloxanes having alkenyl groups onside chains, siloxanes having alkenyl groups at one end and on sidechains, siloxanes having alkenyl groups at both ends and on side chains,and siloxanes having alkenyl groups at branched ends.

Expressed in terms of structural formulas, examples include M^(Vi) ₂Dγ,M₂DγD^(Vi) _(δ), M^(Vi) ₃DγT₁, M^(Vi) ₄DγT₂, M^(Vi) ₂DγD^(Vi) _(δ),M^(Vi) ₂DγQ₁ and M_(α)DγD^(Vi) _(δ)T^(Vi) _(ζ) (wherein γ is 1 to 1,000,preferably 10 to 500, and especially 50 to 400; 6 is 2 to 20, preferably2 to 10, and especially 2 to 5; and ζ is 1 to 20, preferably 1 to 10,and especially 1 to 6). More specific structural examples include M^(Vi)₂D₁₀, M^(Vi) ₂D₁₀₀, M₂D₂₇D^(Vi) ₃, M₂D₉₇D^(Vi) ₃, M₂D₂₆D^(Vi) ₄,M₂D₂₅D^(Vi) ₅, M₂D₂₄D^(Vi) ₆, M₂D₉₆D^(Vi) ₄, M₂D₉₅D^(Vi) ₅, M^(Vi)₃D₁₀₀T₁, M^(Vi) ₄D₁₀₀T₂, M^(Vi) ₂D₉₇D^(Vi) ₁, M^(Vi) ₂D₉₅D^(Vi) ₃ andM₃D₉₃D^(Vi) ₃T^(Vi) ₁.

The vinyl group content (mol/g) is preferably in the range of 0.00001 to0.01 mol/g, and more preferably in the range 0.0001 to 0.001 mol/g.

The organohydrogenpolysiloxane (11) of formula (2) is anorganohydrogenpolysiloxane having at least 2, and preferably 2 to 100,silicon-bonded hydrogen atoms (SiH groups) per molecule. The gel-likesilicone is formed by an addition reaction between the SiH groups on theorganohydrogenpolysiloxane (II) and the vinyl groups on theorganopolysiloxane (I).

The weight-average molecular weight of the organohydrogenpolysiloxane(II) is preferably from 208 to 14,934, and more preferably from 874 to5,000. When the weight-average molecular weight is too small, the alkaliequilibration reaction following the addition reaction may not fullyproceed; when it is too large, the gel may be soft and sticky, making itdifficult to handle.

Specific examples of such organohydrogenhpolysiloxanes (II) includesiloxanes having hydrogen groups at both ends, siloxanes having hydrogengroups on side chains, siloxanes having hydrogen groups at one end andon side chains, siloxanes having hydrogen groups at both ends and onside chains, and siloxanes having hydrogen groups at both ends which arebranched and on side chains.

Expressed in terms of structural formulas, examples include M₂D^(H)_(γ), M₂D_(κ)D^(H), M^(H) ₂D_(κ)D^(H), M^(H) ₃D_(κ)T₁ andM_(θ)D_(κ)D^(H) _(λ), T^(H) _(ν) (wherein i is 1 to 200, preferably 10to 150, and especially 20 to 100; X is 1 to 20, preferably 1 to 10, andespecially 1 to 5; θ is 3 to 22, preferably 3 to 12, and especially 3 to7; and ν is 1 to 20, preferably 1 to 10, and especially 1 to 5). Morespecific structural examples include M^(H) ₂D₁₀, M^(H) ₂D₁₀₀, M₂D₂₇D^(H)₃, M₂D₉₇D^(H) ₃, M₂D₂₆D^(H) ₄, M₂D₂₅D^(H) ₅, M₂D₂₄D^(H) ₆, M₂D₉₆D^(H) ₄,M₂D₉₅D^(H) ₅, M^(H) ₃D₁₀₀T₁, M^(H) ₄D₁₀₀T₂, M^(H) ₂D₉₇D^(H) ₁, M^(H)₂D₉₅D^(H) ₃ and M₃D₉₃D^(H) ₃T^(H) ₁.

The SiH group content is preferably in the range of 0.0001 to 0.1 mol/g,and more preferably in the range 0.0001 to 0.01 mol/g.

The organohydrogenpolysiloxane (11) is used in an amount such that themolar ratio of SiH groups in the organohydrogenpolysiloxane to alkenylgroups in the organopolysiloxane of formula (1) (SiH groups:alkenylgroups) is preferably from 0.8:5 to 2:1, and more preferably from 1:1.5to 1.5:1.

The gel-like silicone (III) which is the first-stage reaction product inthe invention can be synthesized by using a platinum group metalcatalyst to effect a hydrosilylation (addition) reaction between anorganopolysiloxane (I) having a structure of above formula (1) and anorganohydrogenpolysiloxane (II) having a structure of above formula (2).This is a reaction that adds SiH groups in theorganohydrogenpolysiloxane (II) to vinyl groups in theorganopolysiloxane (I) by means of a platinum group metal catalyst.

Here, known catalysts that are used as addition reaction catalysts maybe used as the platinum group metal catalyst. Examples of such platinumgroup metal catalysts include platinum-based, palladium-based,rhodium-based and ruthenium-based catalysts. Of these, the use of aplatinum-based catalyst is especially preferred. Examples of suchplatinum-based catalysts include chloroplatinic acid, alcohol solutionsor aldehyde solutions of chloroplatinic acid, and complexes ofchloroplatinic acid with various olefins or vinylsiloxanes.

These platinum group metal catalysts are added in a catalytic amount. Interms of economic considerations, the weight of the platinum group metalwith respect to the combined amount of the organopolysiloxane (1) andthe organohydrogenpolysiloxane (II) is preferably in the range of 0.1 to100 ppm, and more preferably in the range of 0.5 to 5 ppm.

Synthesis of the gel-like silicone (111) serving as the intermediate inthis invention may be carried out in the absence of solvent or with theuse of a solvent capable of dissolving the organopolysiloxane, such astoluene. However, it is preferable to add a low-viscosity cyclicsiloxane (such as octamethyltetrasiloxane or decamethylpentasiloxane) orlinear diorganopolysiloxane serving as the subsequently describedcompound (IV) prior to the alkali equilibration step, and to use this asthe solvent. Here, the amount of solvent used is preferably less than 7times, more preferably not more than 6 times, and even more preferablynot more than 5.5 times, the combined weight of the organopolysiloxane(I) having a structure of formula (1) and the organohydrogenpolysiloxane(11) having a structure of formula (2). When such a solvent is included,the amount is typically at least 0.5 time, and preferably at least 1time, the combined weight.

Because the reaction due to hydrosilylation proceeds slowly at normaltemperature, the reaction temperature is preferably from 50 to 140° C.,and more preferably from 60 to 120° C., and the reaction time ispreferably 1 to 8 hours, and more preferably 2 to 5 hours.

Next, an oil-like organopolysiloxane (V) can be obtained by furtheradding a compound (IV) having siloxane units of formula (3) to thegel-like silicone (III) obtained by the hydrosilylation reaction, andcarrying out equilibration with an acid or alkaline catalyst.

R¹ ₂SiO_(2/2)  (3)

In this formula, each R¹ is the same or a different group selected fromamong monovalent hydrocarbon groups of 1 to 20 carbon atoms that have noaliphatic unsaturated bonds and alkenyl groups represented by—(CH₂)_(a)—CH═CH₂ (wherein “a” is 0 or an integer from 1 to 6). Thesiloxane of formula (3) has an average degree of polymerization of 3 to2,000.

Here, in formula (3), the monovalent hydrocarbon groups R¹ of 1 to 20carbon atoms, and preferably 1 to 12 carbon atoms, which have noaliphatic unsaturated bonds are exemplified by alkyl groups such asmethyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl and dodecylgroups; cycloalkyl groups such as a cyclohexyl group; aryl groups suchas phenyl, naphthyl and tolyl groups; and any of these groups in whichsome portion of the hydrogen atoms bonded to the carbon atoms aresubstituted with halogen atoms, cyano groups, hydroxyl groups or thelike. R¹ is preferably a methyl group.

The average degree of polymerization of compound (IV) having siloxaneunits of formula (3) is 3 to 2,000, and preferably 3 to 100. When theaverage degree of polymerization is below 3, the mist suppressing effectis low; when the average degree of polymerization is too large, theviscosity becomes too high, making the compound unfit for use. Theaverage degree of polymerization can be determined as thepolystyrene-equivalent weight-average degree of polymerization in GPCanalysis (solvent: toluene).

In addition to siloxane units of formula (3), compound (IV) may alsoinclude (R¹³SiO_(1/2)) structural units, (R¹ ₁SiO_(3/2)) structuralunits (wherein R is as defined above) and (SiO_(4/2)) structural unitssuch that the combined amount thereof with respect to the weight of allthe siloxane units is in the range of preferably 0 to 50 wt %, and morepreferably 0 to 10 wt %.

Examples of compound (IV) having siloxane units of formula (3) includelow-viscosity cyclic siloxanes such as octamethyltetrasiloxane anddecamethylpentasiloxane, linear siloxanes such as M₂D (wherein M and Dare the same as above; and n is an integer from 0 to 200, and preferablyfrom 1 to 50), and branched siloxanes such as M_(2+m)D_(n)T_(m) (whereinM, D and T are the same as above; n is an integer from 0 to 200, andpreferably from 1 to 50; and m is an integer from 1 to 10, andpreferably from 1 to 3).

The amount in which compound (IV) having siloxane units of formula (3)is used should be an amount sufficient to render the gel-like silicone(11) produced by an addition reaction between an organopolysiloxane (I)having a structure of formula (1) and an organohydrogenpolysiloxane (II)having a structure of formula (2) into a liquid state, although thisamount is preferably from 2 to 100 times, more preferably from 3 to 50times, and even more preferably from 3 to 25 times, the number of partsby weight of the crosslinked reaction product of formulas (1) and (2).

As mentioned above, the compound (IV) having siloxane units of formula(3) may be added prior to the addition reaction; alternatively, it maybe added after the addition reaction and alkali equilibration carriedout.

An acid or alkali is used as the catalyst in the equilibration reaction.By using an acid catalyst or an alkaline catalyst, siloxane bonds havinglarge ionicity can be cleaved and recombined, thereby enabling anequilibrated product to be obtained.

Examples of acid catalysts include sulfuric acid, hydrochloric acid,phosphoric acid, activated clay, iron chloride, boric acid,trifluoroacetic acid, methanesulfonic acid and trifluoromethanesulfonicacid.

Examples of alkaline catalysts include KOH, CsOH, NaOH, (CH₃)₄NOH,(n-C₄H₉)₄POH and metal siliconates such as those of potassium orphosphorus.

In the case of harder gels in which the gel-like silicon (III) has ahigh crosslink density, the reaction is preferably carried out using analkaline catalyst under a high temperature.

These catalysts are used in an amount of 10 to 3,000 ppm, and preferably50 to 2,000 ppm.

This reaction by equilibration is preferably carried out at a reactiontemperature of 10 to 160° C., especially 120 to 160° C., for a reactiontime of 1 to 20 hours, especially 2 to 10 hours.

The resulting organopolysiloxane (V) (crosslinked organopolysiloxane) isan oil-like substance that contains no gel. The viscosity at 25° C. ofthis organopolysiloxane (V), as measured with a Brookfield rotationalviscometer, is preferably from 50 to 100,000 mPa·s, and more preferablyfrom 100 to 50,000 mPa·s.

The resulting organopolysiloxane (V) has a silethylene linkage contentper 1,000 moles of siloxane units, as determined by ¹H-NMR, of from 0.1to 50 moles, and preferably from 1 to 30 moles. When the silethylenelinkage content is too low, a mist suppressing effect is not observable;when this content is too high, the viscosity becomes too high, makingmixture difficult.

When the organopolysiloxane (V) (crosslinked organopolysiloxane) has ahigh viscosity, a siloxane composition of the organopolysiloxane (V)diluted with a low-viscosity organopolysiloxane can be prepared. Theviscosity in this case may be set to from 100 to 200,000 mPa·s, andespecially 100 to 10,000 mPa·s. Here, the viscosity is the value at 25°C. measured with a Brookfield rotational viscosity (the same appliesbelow).

The low-viscosity organopolysiloxane used for dilution is preferably alow-viscosity organopolysiloxane which may include unsaturated groupsand has a viscosity at 25° C. of preferably from 1 to 400 mPa·s, andmore preferably from 10 to 200 mPa·s.

Examples of such low-viscosity organopolysiloxanes includedimethylpolysiloxanes having a viscosity of from 1 to 400 mPa·s,dimethylpolysiloxanes having dimethylvinylsiloxy groups at both ends ofthe molecular chain, methylvinylpolysiloxanes having pendant vinylgroups, dimethylpolysiloxanes having dimethylhydroxysilyl groups at bothends, and phenylmethylpolysiloxanes having pendant phenyl groups.

The mist suppressant of the invention is made up of theorganopolysiloxane (V) (i.e., crosslinked organopolysiloxane) obtainedas described above or the foregoing siloxane composition.

The solventless silicone composition for release paper formulated withthe mist suppressant of the invention is preferably an addition-curablesilicone composition containing:

(A) 100 parts by weight of an organopolysiloxane having two or moresilicon-bonded alkenyl groups per molecule,(B) 0.1 to 30 parts by weight of an organohydrogenpolysiloxane havingthree or more silicon-bonded hydrogen atoms (Sill groups) per molecule,(C) a catalytic amount of a platinum group metal catalyst,(D) 0.01 to 20 parts by weight of the mist suppressant and, optionally,(E) a reaction regulator.

The organopolysiloxane having two or more, and preferably from 2 to 50,alkenyl groups per molecule that serves as component (A) is preferably alinear organopolysiloxane that contains alkenyl groups at the endsand/or on side chains thereof and has general formula (4) below.

In formula (4), each R² is the same or a different group selected fromamong unsubstituted or substituted monovalent hydrocarbon groups of 1 to12 carbon atoms that have no aliphatic unsaturated bonds and alkenylgroups represented by —(CH₂)_(q)—CH═CH₂ (wherein q is 0 or an integerfrom 1 to 6), with at least two of all the R² groups being alkenylgroups. The subscript p is from 1 to 1,000.

The unsubstituted or substituted monovalent hydrocarbon groups R² of 1to 10 carbon atoms, and preferably 1 to 6 carbon atoms, that have noaliphatic unsaturated bonds are exemplified by alkyl groups such asmethyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl and dodecylgroups; cycloalkyl groups such as a cyclohexyl group; aryl groups suchas phenyl, naphthyl and tolyl groups; and any of these groups in whichsome portion of the hydrogen atoms bonded to carbon atoms aresubstituted with halogen atoms, cyano groups, hydroxyl groups or thelike. However, to lower the peel strength, it is preferable for at least50 mol % of the total number of R² groups to be methyl groups.

Also, at least 2, preferably from 2 to 50, and more preferably from 2 to10, of all the R² groups are alkenyl groups.

The subscript p is from 1 to 1,000, and preferably from 10 to 300.

The organohydrogenpolysiloxane having three or more silicon-bondedhydrogen atoms (SiH groups) per molecule that serves as component (B) ispreferably one having the following general formula (5).

Here, each R³ is an unsubstituted or substituted monovalent hydrocarbongroup. Also, r is from 1 to 300, and s is from 0 to 150, these beingpresent in a ratio that satisfies the condition r>s.

In formula (5), the R³ groups are unsubstituted or substitutedmonovalent hydrocarbon groups of preferably 1 to 12 carbon atoms, andespecially 1 to 6 carbon atoms, without aliphatic unsaturated bonds.Examples of such monovalent hydrocarbon groups include alkyl groups suchas methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl and dodecylgroups; cycloalkyl groups such as the cyclohexyl group; aryl groups suchas phenyl and naphthyl groups; and halogen-substituted alkyl groups suchas the 3,3,3-trifluoropropyl group.

Also, the subscript “r” is from 1 to 300, preferably 10 to 100, thesubscript “s” is from 0 to 150, preferably 0 to 50, and r and s arepresent in a ratio such that r>s.

Component (B) is included in an amount, per 100 parts by weight ofcomponent (A), of preferably 0.1 to 30 parts by weight, and especially0.1 to 20 parts by weight. The number of moles of silicon-bondedhydrogen atoms in the organohydrogenpolysiloxane (component (B)) withrespect to the total number of moles of alkenyl groups in the alkenylgroup-containing linear organopolysiloxane (component (A)), that is, theSiH group/alkenyl group ratio, is preferably from 1.5 to 2.5, and morepreferably from 1.6 to 2.2. At a SiH group/alkenyl group ratio below1.5, the cure may be incomplete, whereas at a ratio greater than 2.5,the change over time in the peel strength may increase.

The platinum group metal catalyst serving as component (C) may be aknown catalyst that is used as an addition reaction catalyst. Examplesof such platinum group metal catalysts include platinum-based,palladium-based, rhodium-based and ruthenium-based catalysts. Of these,the use of a platinum-based catalyst is especially preferred. Examplesof such platinum-based catalysts include chloroplatinic acid, alcoholsolutions or aldehyde solutions of chloroplatinic acid, and complexes ofchloroplatinic acid with various olefins or vinylsiloxanes.

These platinum group metal catalysts are added in a catalytic amount,with the weight of the platinum group metal included with respect to thecombined amount of components (A) and (B) being preferably from 10 to1,000 ppm, and especially from 10 to 200 ppm.

Component (D) is the above-described mist suppressant. The amount ofthis mist suppressant included is preferably from 0.01 to 20 parts byweight, and especially from 0.1 to 5 parts by weight, per 100 parts byweight of component (A). When the content of mist suppressant is toolow, a mist suppressing effect may not be observable; on the other hand,when it is too high, the viscosity of the overall composition may becometoo high or the peel strength may depart from the target values.

The reaction regulator serving as component (E) is an optionallyincluded ingredient for regulating the catalytic activity of theplatinum group metal catalyst. It is exemplified by various types oforganic nitrogen compounds, organophosphorus compounds, acetylenecompounds, oxime compounds and organochloro compounds. Specific examplesinclude acetylenic alcohols such as 3-methyl-1-butyn-3-ol,3,5-dimethyl-1-hexyn-3-ol, 3-methyl-1-penten-3-ol and phenylbutynol;acetylene compounds such as 3-methyl-3-penten-1-yne and3,5-dimethyl-1-hexyn-3-yne; reaction products of these acetylenecompounds with an alkoxysilane or alkoxysiloxane or with ahydrogensilane or hydrogensiloxane; vinylsiloxanes such astetramethylvinylsiloxane cyclics; organic nitrogen compounds such asbenzotriazoles; and also organophosphorus compounds, oxime compounds,organochloro compounds, etc.

When included, the amount of the reaction regulator (E) should be suchthat a good treatment bath stability is obtained, and in general may beset to from 0 to 3 wt %, and especially 0.01 to 3 wt %, of the totalamount of the composition, with a content of 0.01 to 3 parts by weightper 100 parts by weight of component (C) being preferred.

The mist suppressor-containing, solventless silicone composition forrelease paper may also include the following optional ingredients,within a range that does not detract from the objects of the invention:antioxidants, pigments, stabilizers, antistatic agents, foam inhibitors,tackifiers, and inorganic fillers such as silica.

The mist suppressant-containing, solventless silicone composition forrelease paper can be prepared by uniformly mixing the above ingredientsin the usual manner.

During actual use of the mist suppressant-containing, solventlesssilicone composition for release paper of the invention, the siliconecomposition for release paper may be coated, either as is or followingdilution with a suitable organic solvent, to a weight of 0.01 to 100g/m² onto a base material such as paper or plastic film using a methodof application such as roll coating, reverse coating or gravure coating,and then heated at 50 to 200° C. for 1 to 120 seconds to form a curedfilm on the base material.

Here, examples of the base material include papers such as glassine,polyethylene laminate paper, kraft paper, clay-coated paper andmirror-coated paper; and plastic films made of polypropylene,polyethylene, polyethylene terephthalate, polyvinyl chloride or thelike.

The mist suppressant of the invention does not impart any changewhatsoever in the peel strength of the cured form of the solventlesssilicone composition for release paper.

EXAMPLES

Synthesis Examples, Working Examples and Comparative Examples are givenbelow to more concretely illustrate the invention, although theinvention is not limited by these Examples. The viscosities mentionedbelow are all values measured at 25° C. using a Brookfield rotationalviscometer.

The symbols used in the following Examples to indicate siloxanecompositions denote the following units.

M: (CH₃)₃SiO_(1/2)

M^(H): (CH₃)₂HSiO_(1/2)

M^(Vi): (Cl₂═CH)(CH₃)₂SiO_(1/2)

D: (CH₃)₂SiO_(2/2)

D^(H): (CH₃)HSiO_(2/2)

D^(Vi): (CH₂═CH)(CH₃)SiO_(2/2)

T^(Vi): (CH₂═CH)SiO_(3/2)

Q: SiO_(4/2)

Synthesis Example 1

The linear methylhydrogenpolysiloxane represented by M^(H) ₂D₂₉ (10 g)and 48 g of the linear vinylmethylpolysiloxane with branches representedby M₂D^(Vi) _(1.4)D₁₄₇T^(Vi) ₁ (SiH groups:vinyl groups=1 mole:1.17moles) were mixed together in 280 g of decamethylpentasiloxane (Ds),following which a platinum catalyst to which vinylmethylpolysiloxane wascoordinated was added in an amount corresponding to a platinum weight of2 ppm and the temperature was raised. Gelling occurred at 50 to 60° C.,at which point the reaction was stopped, 200 ppm of KOH was added, andthe equilibration reaction was carried out at 150° C. for 6 hours. Thetemperature was lowered to 80° C., after which neutralization wascarried out by adding 0.2 g of ethylene chlorohydrin. The resultingproduct was a high-viscosity oil-like substance having a viscosity of126,500 mPa·s. The amount of silethylene linkages per 1,000 moles ofsiloxane units, as determined by ¹H-NMR analysis, was 1.9 moles.

Synthesis Example 2

The linear methylhydrogenpolysiloxane represented by M^(H) ₂D₅₉ (4.1 g)and 12.24 g of the silicone resin represented by M_(0.74)M^(Vi)_(0.08)Q₁(SiH groups:vinyl groups=1 mole:4.2 moles) were mixed togetherin 33.5 g of linear dimethylpolysiloxane represented by M₂D₇₉ and 25.2 gof decamethylpentasiloxane (Ds), following which a platinum catalyst towhich vinylmethylpolysiloxane was coordinated was added in an amountcorresponding to a platinum weight of 2 ppm and the temperature wasraised. Gelling occurred at 50 to 60° C., at which point the reactionwas stopped, 29.9 g of the linear divinyl-terminateddimethylpolysiloxane represented by M^(Vi) ₂D_(585.32) was added andstirring was thoroughly carried out. Next, 1,200 ppm of KOH was added,and the equilibration reaction was carried out at 150° C. for 6 hours.The temperature was lowered to 80° C., after which neutralization wascarried out by adding 0.2 g of ethylene chlorohydrin. Vacuumconcentration was then carried at 150° C. and 2 mmHg for 2 hours. Theresulting product was an oil-like substance having a viscosity of 1,550mPa·s. The amount of silethylene linkages per 1,000 moles of siloxaneunits, as determined by ¹H-NMR analysis, was 6.2 moles.

Synthesis Example 3

The linear dimethylhydrogenpolysiloxane represented by M^(H) ₂D_(31.97)(11 g) and 49.3 g of the linear vinylmethylpolysiloxane represented byM₂D^(Vi) _(2.4)D_(150.4) (SiH groups:vinyl groups=1 mole:1.17 moles)were mixed together in 422 g of the linear dimethylpolysiloxanerepresented by M₂D₂₄, following which a platinum catalyst to whichlinear vinylmethylpolysiloxane was coordinated was added in an amountcorresponding to a platinum weight of 2 ppm and the temperature wasraised. Gelling occurred at 50 to 60° C., at which point the reactionwas stopped, another 870 of the linear dimethylpolysiloxane representedby M₂D₂₄ was added thereto and the gel was stirred while being mashed ina homogenizing mixer at 2,000 rpm for 3 hours. The resulting product hada viscosity of 280 mPa·s, but a fine gel remained. The amount ofsilethylene linkages per 1,000 moles of siloxane units in thecrosslinked product, as determined by ¹H-NMR analysis, was 11.3 moles.

Synthesis Example 4

The gel-containing silicone oil synthesized in Synthesis Example 3 wasfiltered with filter paper. The yield of the resulting oil was about 20wt % of the oil in Synthesis Example 3, and the viscosity was 41 mPa·s.Upon visual observation, no gel was observed therein

Synthesis Example 5

The linear dimethylhydrogenpolysiloxane represented by M₂D_(31.97)D^(II)₅ (51 g) and 49 g of the linear vinylmethylpolysiloxane represented byM₂D^(Vi) ₄D_(148.56) (SiH groups:vinyl groups=1 mole:0.19 mole) weremixed together, following which a platinum catalyst to which linearvinylpolysiloxane was coordinated was added in an amount correspondingto a platinum weight of 2 ppm and the temperature was raised. After thereaction had been carried out at 90° C. for 3 hours, the amount of SiHgroups was 0.085 mol/100 g and all of the vinyl groups had reacted. Thevolatile ingredients were then vacuum concentrated at 120° C. and 2 mmHgfor 3 hours. The resulting silicone oil had a viscosity of 2,400 mPa·s.

The evolution of hydrogen gas over time by this silicone oil wasconfirmed. The amount of silethylene linkages per 1,000 moles ofsiloxane units, as determined by ¹H-NMR analysis, was 74.4 moles.

When 50 g of the compounds from the respective Synthesis Examples weremixed together with 100 g of the compound of formula (6) below and 2 gof the compound of formula (7) below and stirred at 80° C., changes inviscosity were not observed for the compounds from Synthesis Examples 1and 2, but gelling occurred in the systems in which the compounds ofSynthesis Example 3, 4 and 5 had been mixed.

Working Examples 1 to 3, Comparative Examples 1 to 4

Various organopolysiloxane compositions were prepared as described belowby adding the various mist suppressants produced in the SynthesisExamples to the base composition shown below, and the preparedcompositions were cured.

The amount of mist generated, peel strength and subsequent adhesionratio for the organopolysiloxane compositions were measured by themethods described below. The viscosity of the final composition wasmeasured by the method described above. There were no problems withcurability for any of the organopolysiloxane compositions.

<Method of Preparing Organopolysiloxane Composition>

Various organopolysiloxane compositions were prepared by using as thebase composition 100 parts by weight of the dimethylpolysiloxane offormula (6) below

having vinyldimethylsiloxy groups at both ends, 2.7 parts by weight ofthe methylhydrogenpolysiloxane of formula (7) below

0.4 part by weight of ethynylcyclohexanol and 2 parts by weight of acomplex salt of chloroplatinic acid and vinylsiloxane (platinum weightbasis, 100 ppm), adding to this composition 1 or 2 parts by weight ofthe mist suppressants prepared in the above Synthesis Examples, andthoroughly stirring. The formulated compositions are shown in Table 1.

<Method of Measuring Amount of Mist Generated>

The test sample, 1.6 g, was coated onto the topmost roller in a MistingTester (Toyo Seiki Seisaku-Sho, Ltd.), the three rollers were rotated ata speed of 1,400 rpm, and the amount of mist generated was measured withthe DustTrak Aerosol Monitor, Model 8520, from TSI Incorporated. Themist was collected by positioning one opening of a vinyl tube having a 7mm inside diameter 15 cm directly above the topmost roller, andconnecting the other opening in the vinyl tube to the intake of theDustTrak. Measurement was carried out for 180 seconds and the maximumvalue was recorded. The maximum detection limit for the DustTrak is 150mg/m³. The results are shown in Table 1.

<Method of Curing the Organopolysiloxane Composition>

Following preparation, the organopolysiloxane composition was appliedonto polyethylene laminate paper as the base material to a coatingweight of 0.9 to 1.1 g/m², and heated for 30 seconds in a 140° C. hotair dryer. The resulting coated paper was used as the separator in thefollowing measurements.

<Surface State of Coated Sample>

The surface of the silicone separator obtained by curing theorganopolysiloxane composition by the above method was visuallyexamined. Separators free of any coating problems were rated as “Good,”and separators having surface irregularities or foreign matter wererated as “NG.” The results are shown in Table 1

<Method of Measuring Peel Strength>

A test specimen was prepared by holding a silicone separator obtained bythe curing method described above at 25° C. for 20 hours, then bondingTESA-7475 tape thereto and holding the separator with the attached tapefor 20 hours in a 70° C. dryer under an applied load of 20 g/m². Using atensile tester, the TESA-7475 tape was peeled from the specimen at anangle of 180° and a rate of 0.3 m/min. The force required to peel offthe tape was measured and treated as the peel strength (N/25 mm). Theresults are shown in Table 1.

<Method of Measuring Subsequent Adhesion Ratio>

The TESA-7475 tape following the above peel test was attached to astainless steel plate, and bonded under applied pressure by a singleback-and-forth pass with a 2 kg tape roller, after which it was peeledoff at an angle of 180° and a rate of 0.3 m/min using a tensile tester,and the force required for re-peeling was measured. The subsequentadhesion ratio was calculated as follows. The results are shown in Table1.

Subsequent adhesion ratio (%)=(re-peel strength+peel strength)×100

TABLE 1 Contents of organopolysiloxane composition Working ExampleComparative Example (pbw) 1 2 3 1 2 3 4 Mist suppressant SynthesisExample 1 1 2 — — — — — Synthesis Example 2 — — 2 — — — — SynthesisExample 3 — — — 2 — — — Synthesis Example 4 — — — — 2 — — SynthesisExample 5 — — — — — 2 — Dimethylpolysiloxane capped at both 100 100 100100 100 100 100 ends with vinyldimethylsiloxy groupsMethylhydrogenpolysiloxane 2.7 2.7 2.7 2.7 2.7 2.7 2.7Ethynylcyclohexanol 0.4 0.4 0.4 0.4 0.4 0.4 0.4 Complex salt ofchloroplatinic acid 2 2 2 2 2 2 2 and vinylsiloxane Evaluation ResultsAmount of mist generated 28 15 35 38 125 91 150 (maximum value for 180seconds; mg/m³) Surface state of coated sample good good good NG goodgood good Peel strength (N/25 mm) 10 10 10 15 10 17 10 Subsequentadhesion ratio (%) 97 96 96 89 95 95 97

1. A crosslinked organopolysiloxane comprising an organopolysiloxanewhich contains 6.2 to 50 moles of silethylene linkages per 1,000 molesof siloxane units and is obtained by adding, to a gel-like siliconeprepared by hydrosilylation of an organopolysiloxane having a structureof formula (1) below with an organohydrogenpolysiloxane having astructure of formula (2) belowM_(α)M^(Vi) _(β)D_(γ)D^(Vi) _(δ)T_(ε)T^(Vi) _(ζ)Q_(η)  (1)M_(θ)M^(H) _(τ)D_(κ)D^(H) _(λ)T_(μ)T^(H) _(ν)  (2) (wherein M isR₃SiO_(1/2), M^(Vi) is R₂PSiO_(1/2), D is R₂SiO_(2/2), D^(Vi) isRPSiO_(2/2), T is RSiO_(3/2), T^(Vi) is PSiO_(3/2), M^(H) isR₂HSiO_(1/2), D^(H) is RHSiO_(2/2), T^(H) is HSiO_(3/2) and Q isSiO_(4/2), each R being independently an unsubstituted or substitutedmonovalent hydrocarbon group of 1 to 12 carbon atoms that has noaliphatic unsaturated bonds and P being an alkenyl group represented by—(CH₂)_(a)—CH═CH₂ (where “a” is 0 or an integer from 1 to 6); and α, β,γ, δ, ε, ζ, η, θ, τ, κ, λ, τ and ν are each independently 0 or apositive number, with the provisos that β, δ and ζ are not all 0,β+δ+ζ≥2, τ, λ and ν are not all 0, and τ+λ+ν≥2), a compound havingsiloxane units of formula (3) belowR¹ ₂SiO_(2/2)  (3) (wherein each R¹ is the same or a different groupselected from among monovalent hydrocarbon groups of 1 to 20 carbonatoms that have no aliphatic unsaturated bonds and alkenyl groupsrepresented by —(CH₂)_(a)—CH═CH₂ (where “a” is 0 or an integer from 1 to6); and an average degree of polymerization of the siloxane of formula(3) is from 3 to 2,000 in the compound having siloxane units of formula(3)) and carrying out equilibration.
 2. The crosslinkedorganopolysiloxane of claim 1 wherein, in formula (1), 1≤α+γ+ε+η≤1,000and, in formula (2), 1≤θ+κ+μ≤200.
 3. The crosslinked organopolysiloxaneof claim 2 wherein, in formula (1), 1≤γ≤1,000 and, in formula (2),1≤κ≤200.
 4. The crosslinked organopolysiloxane of any one of claims 1 to3, wherein the compound having siloxane units of formula (3) is anorganosiloxane selected from among octamethyltetrasiloxane,decamethylpentasiloxane, linear siloxanes of the formula M₂D_(n) (Mbeing an R₃SiO_(1/2) unit, D being an R₂SiO_(2/2) unit, each R beingindependently an unsubstituted or substituted monovalent hydrocarbongroup of 1 to 12 carbon atoms which has no aliphatic unsaturated bonds,and n being an integer from 0 to 200) and branched siloxanes of theformula M_(2+m)D_(n)T_(m) (M, D and n being the same as above, T beingan RSiO_(3/2) unit, R being the same as above, and m being an integerfrom 1 to 10).
 5. The crosslinked organopolysiloxane of claim 1, whereinthe organopolysiloxane of formula (1) has a weight-average molecularweight of 260 to 74,186 and the organohydrogenpolysiloxane of formula(2) has a weight-average molecular weight of 208 to 14,934.
 6. Asiloxane composition obtained by diluting the crosslinkedorganopolysiloxane of claim 1 with a low-viscosity organopolysiloxanehaving a viscosity at 25° C. of 1 to 400 mPa·s.
 7. A mist suppressantcomprising the crosslinked organopolysiloxane of claim 1 or the siloxanecomposition of claim
 6. 8. A solventless silicone composition forrelease paper, comprising: (A) 100 parts by weight of anorganopolysiloxane having two or more silicon-bonded alkenyl groups permolecule, (B) 0.1 to 30 parts by weight of an organohydrogenpolysiloxanehaving three or more silicon-bonded hydrogen atoms per molecule, (C) acatalytic amount of a platinum group metal catalyst, and (D) 0.01 to 20parts by weight of the mist suppressant of claim 7.